Quicker way of adding faces?
Select the prism and press P to separate it. Being in Edit Mode add an Array Modifier to the prism and set up the proper relative offset values. Check the Wire and Draw All checkboxes in Display panel of the Object Data header to help you match the prisms with a grid segments properly. Increase the modifier's count number and apply it. Join meshes with Ctrl+J. In Edit Mode select one of the edges as pictured below, go to Select-->Checker Deselect, increase the offset if needed and delete selected edges to cut the holes for prisms. In the end select the whole object with A, then press W-->Remove Doubles. You may also recalculate normals with Ctrl+N.